Researchers use stirrers for many laboratory applications, from dissolving powders to mixing reagents. To get the right results, it takes more than placing a stir bar into a vessel and turning on the stirring device.
Today’s devices accommodate simple and specialized applications. For example, Laura Geenen, product manager at Bel-Arts Products (Wayne, NJ), says, “We make a large volume stirrer that stirs a 55-gallon drum for industrial uses.”
Special stirring situations
Large-volume or highly viscous mixtures demand special requirements from a stirrer. For example, rare-earth magnets work better for viscous mixtures. In addition, small volumes require special attention. “Sample volumes are getting smaller in life science labs,” says Geenen. For instance, she mentions stirrers for microplates. “We can stir in five-milliliter vials, and tiny volumes can be harder to stir than large ones.”
The magnetic stir bar plays as big a part as the stirring platform, and different mixtures need different bars. “Our new Spinfinity stir bar,” says Geenen, “has a hard-plastic casing that is designed for use in granular slurries.” This bar’s casing is more durable than a Teflon stir bar. “It is resistant to flaking,” Geenen says.
Justin Whiteman, senior scientist in product development at Stiefel, a GSK company (Research Triangle Park, NC), uses stirrers to develop semisolid liquids for topical application. “We use stirring elements for small-scale production units,” he says. “We try different paddle and blade configurations to generate the formulations.” To make that development as consistent as possible, Whiteman says, “we like electrically driven stirrers because they maintain speed and increase torque as required.”
The overhead approach
When mixing needs more than a magnetic stirrer, some devices take an overhead approach. When asked what is important for the user of an overhead stirrer, Stuart Gibb, director of sales for laboratory and analytical equipment at IKA Works (Wilmington, NC), says, “Users require systems that are reliable, deliver accurate mixing, and afford them the ability to work with varying viscosities and volumes safely.”
These characteristics accurately describe IKA Works’ new Eurostar line. For example, these units include the first-ever wireless controller (WiCo). The removable WiCo controller allows the user to control and monitor every function of the mixer in real time,” Gibb says. “The WiCo controller with its USB interface allows realtime monitoring of speed/torque changes, temperature, and many more parameters.”
Beyond convenience, the WiCo controller enhances lab safety. “The wireless control can be removed from the Eurostar, allowing total control even in a completely enclosed hood from up to 30 feet away,” Gibb explains.
Pointers on purchasing
When buying a new stirrer, Geenen offer some key tips. “Know what kind of vessels you’ll be using and their size,” she says. To get the right bar, Bel-Arts Products is launching an app that Geenen says will “select by size and shape of your vessel, like a round-bottom flask.” She points out that stir bars come in many sizes and shapes. So for your next stirring needs, pick the right device and stir bar pair to ensure the desired results.